a) Field of the invention
This invention relates to end bearings for a one-way clutches, a manufacturing process thereof, and a one-way clutch provided with at least one of such end bearings.
b) Description of the Related Art
FIG. 7 is an axial cross-sectional view of one example of one-way clutch assemblies. Arranged between an inner ring 12 and an outer ring 13 are sprags 21, a ribbon spring 22 urging the sprags 21, and cages 23, 24 holding the sprags 21 and the ribbon spring 22 in place. End bearings 1, 1 are arranged on axially opposite sides of these sprags, ribbon spring and cages. The end bearings 1, 1 has a function to prevent occurrence of minute eccentricity which would otherwise take place between the inner ring 12 and the outer ring 13 due to vibrations from an engine or the like, and hence, to protect the sprags 21 and the ribbon spring 22. Further, retainer plates 14, 14 are also arranged on axially outer sides of the respective end bearings 1, 1. These retainer plates 14, 14 are maintained in sliding contact with their corresponding counterpart members 15, 15 via thrust bearings 16, 16, respectively. Designated at numeral 17 is an oilway formed through the inner ring 12 to supply lube oil into a space in which the sprags 21 are arranged.
With reference to FIG. 8 through FIG. 10, the right-hand end bearing 1 will be described. FIG. 8 is an axial cross-sectional view of the right-hand end bearing 1. The end bearing 1 has an outer peripheral wall 4, an inner peripheral wall 3 and a holding portion 5. The outer peripheral wall 4 is formed by an outer peripheral flange and is arranged in contact with an inner periphery of the outer ring 13, while the inner peripheral wall 3 is formed by an inner peripheral flange and is arranged in contact with an outer periphery of the inner ring 12. Incidentally, FIG. 9 shows the right-hand end bearing 1 as viewed in the direction of arrow A of FIG. 8, and FIG. 10 illustrates the right-hand end bearing 1 as viewed in the direction of arrow B of FIG. 8.
As the end bearings 1, 1 are maintained in sliding contact with the inner ring 12 and the outer ring 13, it is necessary to supply lube oil to avoid occurrence of seizure. However, the end bearings 1, 1 are arranged to prevent occurrence of minute eccentricity which would otherwise take place between the inner ring 12 and the outer ring 13, so that a clearance between the inner ring 12 and the outer ring 13 is set small. This small clearance makes it difficult to supply lube oil, or tends to develop viscous resistance. With a view to overcoming this problem, some constructions have been invented, including a construction in which as shown in FIG. 11, spiral grooves 8 are formed on an inner peripheral wall 3 to assure a flow of lube oil on and along the inner peripheral wall 3 and another construction in which as illustrated in FIG. 12, dynamic pressure producing recesses 9 are formed on an inner peripheral wall 3 to avoid occurrence of viscous resistance by lube oil.
However, the arrangement of the above-described grooves 8 or dynamic pressure producing recesses 9 reduces the area of contact with the inner ring 12 or the outer ring 13, so that the local bearing stress becomes somewhat higher. Under some stringent use conditions such as high vibrations and/or a high circumferential speed, a problem is expected to arise in strength.
An object of the present invention is, therefore, to provide an end bearing at low cost for a one-way clutch, which end bearing hardly produces local bearing stress while reducing drag torque associated with the viscosity of lube oil and also maintaining lubricity.
Another object of the present invention is to provide a one-way clutch provided with one or two of such end bearings.
A further object of the present invention is to provide a process for manufacturing such end bearings are low cost.
To achieve the above-described objects, the present invention, in one aspect thereof, provides an end bearing for a one-way clutch, said end bearing being provided with non-through-holes on at least one of an inner peripheral wall and outer peripheral wall thereof, wherein the non-through-holes are arranged on and along plural imaginary lines extending at a predetermined angle relative to a circumferential direction of said at least one peripheral wall. The non-through-holes may preferably be minute non-through-holes each of which has a diameter in a range of from 0.1 to 0.4 mm. As advantages of these end bearings, they are low in drag torque and excellent in lubricity, and they hardly produce local bearing stress.
In another aspect of the present invention, the present invention also provides a one-way clutch comprising sprags and two end bearings as described above. These end bearings are arranged on axially opposite sides of the sprags, respectively, such that plural imaginary lines, on and along which non-through-holes of one of the end bearings are arranged, and plural imaginary lines, on and along which non-through-holes of the other end bearing are arranged, all extend in the same direction. This one-way clutch allows to use end bearings of the same type as the bearings to be arranged on the axially opposite sides of the sprags. This can bring about an advantage that manufacture of defective products, such as misassembling or assembling in an opposite direction, can be avoided.
In a further aspect of the present invention, there is also provided a one-way clutch comprising an end bearing as described above and an inner ring with an opening of an oilway formed at a sliding surface thereof with the end bearing. This one-way clutch is provided with a wider area of contact with sprags. Bearing stress is thus reduced, thereby making it possible to use fewer sprags.
In a still further aspect of the present invention, there is also provided a manufacturing process of an end bearing as described above for a one-way clutch, which comprises machining non-through-holes concurrently with formation of the end bearing on a press. This manufacturing process has an advantage that the end bearing can be produced at low cost.
In the one-way clutch having the inner ring with the opening of the oilway formed at the sliding surface thereof with the end bearing, the end bearing is arranged on one side of its sprags. It is to be noted that a second end bearing can be additionally arranged on the opposite side of the sprags.